Middle three digits: Difference between revisions
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The middle three digits of 12345 are: 234 |
The middle three digits of 12345 are: 234 |
||
The middle three digits of 1234567 are: 345 |
The middle three digits of 1234567 are: 345 |
||
The middle three digits of 987654321 are: |
The middle three digits of 987654321 are: 654 |
||
The middle three digits of 10001 are: |
The middle three digits of 10001 are: 000 |
||
The middle three digits of -10001 are: |
The middle three digits of -10001 are: 000 |
||
The middle three digits of -123 are: |
The middle three digits of -123 are: 123 |
||
The middle three digits of -100 are: |
The middle three digits of -100 are: 100 |
||
The middle three digits of 100 are: 100 |
The middle three digits of 100 are: 100 |
||
The middle three digits of -12345 are: 234 |
The middle three digits of -12345 are: 234 |
||
The middle three digits of 1 are: Not enough digits. |
The middle three digits of 1 are: Not enough digits. |
||
The middle three digits of 2 are: Not enough digits. |
The middle three digits of 2 are: Not enough digits. |
||
The middle three digits of -1 are: Not enough digits. |
The middle three digits of -1 are: Not enough digits. |
||
The middle three digits of -10 are: Not enough digits. |
The middle three digits of -10 are: Not enough digits. |
||
The middle three digits of 2002 are: |
The middle three digits of 2002 are: Even number of digits. |
||
The middle three digits of -2002 are: |
The middle three digits of -2002 are: Even number of digits. |
||
The middle three digits of 0 are: Not enough digits. |
The middle three digits of 0 are: Not enough digits. |
||
</pre> |
</pre> |
||
Revision as of 12:09, 21 April 2015
You are encouraged to solve this task according to the task description, using any language you may know.
The task is to:
- “Write a function/procedure/subroutine that is called with an integer value and returns the middle three digits of the integer if possible or a clear indication of an error if this is not possible.”
- Note: The order of the middle digits should be preserved.
Your function should be tested with the following values; the first line should return valid answers, those of the second line should return clear indications of an error:
123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345 1, 2, -1, -10, 2002, -2002, 0
Show your output on this page.
Ada
<lang Ada>with Ada.Text_IO;
procedure Middle_Three_Digits is
Impossible: exception;
function Middle_String(I: Integer; Middle_Size: Positive) return String is
S: constant String := Integer'Image(I);
First: Natural := S'First;
Full_Size, Border: Natural;
begin
while S(First) not in '0' .. '9' loop -- skip leading blanks and minus
First := First + 1;
end loop;
Full_Size := S'Last-First+1;
if (Full_Size < Middle_Size) or (Full_Size mod 2 = 0) then
raise Impossible;
else
Border := (Full_Size - Middle_Size)/2;
return S(First+Border .. First+Border+Middle_Size-1);
end if;
end Middle_String;
Inputs: array(Positive range <>) of Integer :=
(123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345,
1, 2, -1, -10, 2002, -2002, 0);
Error_Message: constant String := "number of digits must be >= 3 and odd";
package IIO is new Ada.Text_IO.Integer_IO(Integer);
begin
for I in Inputs'Range loop
IIO.Put(Inputs(I), Width => 9);
Ada.Text_IO.Put(": ");
begin
Ada.Text_IO.Put(Middle_String(Inputs(I), 3));
exception
when Impossible => Ada.Text_IO.Put("****" & Error_Message & "****");
end;
Ada.Text_IO.New_Line;
end loop;
end Middle_Three_Digits;</lang>
- Output:
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1: ****number of digits must be >= 3 and odd****
2: ****number of digits must be >= 3 and odd****
-1: ****number of digits must be >= 3 and odd****
-10: ****number of digits must be >= 3 and odd****
2002: ****number of digits must be >= 3 and odd****
-2002: ****number of digits must be >= 3 and odd****
0: ****number of digits must be >= 3 and odd****
Aime
<lang aime>void m3(integer i) {
text s;
s = itoa(i);
if (character(s, 0) == '-') {
s = delete(s, 0);
}
if (length(s) < 3) {
v_integer(i);
v_text(" has not enough digits\n");
} elif (length(s) & 1) {
o_winteger(9, i);
o_text(": ");
o_text(cut(s, length(s) - 3 >> 1, 3));
o_byte('\n');
} else {
v_integer(i);
v_text(" has an even number of digits\n");
}
}
void middle_3(...) {
integer i;
i = 0;
while (i < count()) {
m3($i);
i += 1;
}
}
integer main(void) {
middle_3(123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100,
-12345, 1, 2, -1, -10, 2002, -2002, 0);
return 0;
}</lang>
- Output:
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1 has not enough digits
2 has not enough digits
-1 has not enough digits
-10 has not enough digits
2002 has an even number of digits
-2002 has an even number of digits
0 has not enough digits
ALGOL 68
<lang algol68># we define a UNION MODE so that our middle 3 digits PROC can #
- return either an integer on success or a error message if #
- the middle 3 digits couldn't be extracted #
MODE EINT = UNION( INT # success value #, STRING # error message # );
- PROC to return the middle 3 digits of an integer. #
- if this is not possible, an error message is returned #
- instead #
PROC middle 3 digits = ( INT number ) EINT: BEGIN
# convert the absolute value of the number to a string with the # # minumum possible number characters # STRING digits = whole( ABS number, 0 ); INT len = UPB digits;
IF len < 3
THEN
# number has less than 3 digits #
# return an error message #
"number must have at least three digits"
ELIF ( len MOD 2 ) = 0
THEN
# the number has an even number of digits #
# return an error message #
"number must have an odd number of digits"
ELSE
# the number is suitable for extraction of the middle 3 digits #
INT first digit pos = 1 + ( ( len - 3 ) OVER 2 );
# the result is the integer value of the three digits #
( ( ( ABS digits[ first digit pos ] - ABS "0" ) * 100 )
+ ( ( ABS digits[ first digit pos + 1 ] - ABS "0" ) * 10 )
+ ( ( ABS digits[ first digit pos + 2 ] - ABS "0" ) )
)
FI
END; # middle 3 digits #
main: (
# test the middle 3 digits PROC #
[]INT test values = ( 123, 12345, 1234567, 987654321
, 10001, -10001, -123, -100
, 100, -12345
# the following values should fail #
, 1, 2, -1, -10, 2002, -2002, 0
);
FOR test number FROM LWB test values TO UPB test values DO
CASE middle 3 digits( test values[ test number ] )
IN
( INT success value ): # got the middle 3 digits #
printf( ( $ 11z-d, " : ", 3d $
, test values[ test number ]
, success value
)
)
,
( STRING error message ): # got an error message #
printf( ( $ 11z-d, " : ", n( UPB error message )a $
, test values[ test number ]
, error message
)
)
ESAC;
print( ( newline ) )
OD
)</lang>
- Output:
123 : 123
12345 : 234
1234567 : 345
987654321 : 654
10001 : 000
-10001 : 000
-123 : 123
-100 : 100
100 : 100
-12345 : 234
1 : number must have at least three digits
2 : number must have at least three digits
-1 : number must have at least three digits
-10 : number must have at least three digits
2002 : number must have an odd number of digits
-2002 : number must have an odd number of digits
0 : number must have at least three digits
AutoHotkey
<lang AutoHotkey>Numbers:="123,12345,1234567,987654321,10001,-10001,-123,-100,100,-12345,1,2,-1,-10,2002,-2002,0" Loop, parse, Numbers, `, { if A_LoopField is not number log := log . A_LoopField . "`t: Not a valid number`n" else if((d:=StrLen(n:=RegExReplace(A_LoopField,"\D")))<3) log := log . A_LoopField . "`t: Too short`n" else if(!Mod(d,2)) log := log . A_LoopField . "`t: Not an odd number of digits`n" else log := log . A_LoopField . "`t: " . SubStr(n,((d-3)//2)+1,3) . "`n" } MsgBox % log</lang>
- Output:
123 : 123 12345 : 234 1234567 : 345 987654321 : 654 10001 : 000 -10001 : 000 -123 : 123 -100 : 100 100 : 100 -12345 : 234 1 : Too short 2 : Too short -1 : Too short -10 : Too short 2002 : Not an odd number of digits -2002 : Not an odd number of digits 0 : Too short
AWK
<lang AWK>#!/bin/awk -f
- use as: awk -f middle_three_digits.awk
BEGIN { n = split("123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1 -10 2002 -2002 0", arr)
for (i=1; i<=n; i++) { if (arr[i] !~ /^-?[0-9]+$/) { printf("%10s : invalid input: not a number\n", arr[i]) continue }
num = arr[i]<0 ? -arr[i]:arr[i] len = length(num)
if (len < 3) { printf("%10s : invalid input: too few digits\n", arr[i]) continue }
if (len % 2 == 0) { printf("%10s : invalid input: even number of digits\n", arr[i]) continue }
printf("%10s : %s\n", arr[i], substr(num, len/2, 3)) } } </lang>
- Output:
123 : 123
12345 : 234
1234567 : 345
987654321 : 654
10001 : 000
-10001 : 000
-123 : 123
-100 : 100
100 : 100
-12345 : 234
1 : invalid input: too few digits
2 : invalid input: too few digits
-1 : invalid input: too few digits
-10 : invalid input: too few digits
2002 : invalid input: even number of digits
-2002 : invalid input: even number of digits
0 : invalid input: too few digits
BASIC
Applesoft BASIC
<lang ApplesoftBasic>100 DEF FN L(N) = LEN(STR$(INT(ABS(N)))) 110 DEF FN N(N) = VAL(MID$(STR$(INT(ABS(N))),(FN L(N)-1)/2,3)) 120 DEF FN EVEN(N) = INT(N/2) = N/2 130 FOR I = 1 TO 20 140 READ N 150 PRINT N":", 160 GOSUB 100"MIDDLE THREE DIGITS 170 PRINT R$ 180 NEXT 190 END 200 R$ = "" 210 IF FN EVEN(FN L(N)) THEN R$ = "?EVEN," 220 IF FN L(N) < 3 THEN R$ = R$ + "ONLY " + STR$(FN L(N)) + " DIGIT" + MID$("S",FN L(N) - 1, 1) 230 IF RIGHT$(R$, 1) = "," THEN R$ = LEFT$(R$, LEN(R$) - 1) : RETURN 240 IF LEFT$(R$, 1) = "?" THEN RETURN 250 IF R$ <> "" THEN R$ = "?" + R$ : RETURN 260 R$ = STR$(FN N(N)) 270 IF LEN(R$) = 1 THEN R$ = "00" + R$ 280 IF LEN(R$) = 2 THEN R$ = "0" + R$ 290 RETURN 300 DATA123,12345,1234567,987654321,10001,-10001,-123,-100,100,-12345 310 DATA1,2,-1,-10,2002,-2002,0 </lang>
- Output:
123: 123 12345: 234 1234567: 345 987654321: 654 10001: 000 -10001: 000 -123: 123 -100: 100 100: 100 -12345: 234 1: ?ONLY 1 DIGIT 2: ?ONLY 1 DIGIT -1: ?ONLY 1 DIGIT -10: ?EVEN,ONLY 2 DIGITS 2002: ?EVEN -2002: ?EVEN 0: ?ONLY 1 DIGIT
FBSL
<lang qbasic>#APPTYPE CONSOLE
DIM numbers AS STRING = "123,12345,1234567,987654321,10001,-10001,-123,-100,100,-12345,1,2,-1,-10,2002,-2002,0" DIM dict[] = Split(numbers, ",") DIM num AS INTEGER DIM num2 AS INTEGER DIM powered AS INTEGER
FOR DIM i = 0 TO COUNT(dict) - 1
num2 = dict[i]
num = ABS(num2)
IF num < 100 THEN
display(num2, "is too small")
ELSE
FOR DIM j = 9 DOWNTO 1
powered = 10 ^ j
IF num >= powered THEN
IF j MOD 2 = 1 THEN
display(num2, "has even number of digits")
ELSE
display(num2, middle3(num, j))
END IF
EXIT FOR
END IF
NEXT
END IF
NEXT
PAUSE
FUNCTION display(num, msg)
PRINT LPAD(num, 11, " "), " --> ", msg
END FUNCTION
FUNCTION middle3(n, pwr)
DIM power AS INTEGER = (pwr \ 2) - 1
DIM m AS INTEGER = n
m = m \ (10 ^ power)
m = m MOD 1000
IF m = 0 THEN
RETURN "000"
ELSE
RETURN m
END IF
END FUNCTION</lang> Output
123 --> 123
12345 --> 234
1234567 --> 345
987654321 --> 654
10001 --> 000
-10001 --> 000
-123 --> 123
-100 --> 100
100 --> 100
-12345 --> 234
1 --> is too small
2 --> is too small
-1 --> is too small
-10 --> is too small
2002 --> has even number of digits
-2002 --> has even number of digits
0 --> is too small
Press any key to continue...
PureBasic
<lang purebasic>Procedure.s middleThreeDigits(x.q)
Protected x$, digitCount
If x < 0: x = -x: EndIf
x$ = Str(x) digitCount = Len(x$) If digitCount < 3 ProcedureReturn "invalid input: too few digits" ElseIf digitCount % 2 = 0 ProcedureReturn "invalid input: even number of digits" EndIf
ProcedureReturn Mid(x$,digitCount / 2, 3)
EndProcedure
If OpenConsole()
Define testValues$ = "123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1 -10 2002 -2002 0" Define i, value.q, numTests = CountString(testValues$, " ") + 1 For i = 1 To numTests value = Val(StringField(testValues$, i, " ")) PrintN(RSet(Str(value), 12, " ") + " : " + middleThreeDigits(value)) Next Print(#crlf$ + #crlf$ + "Press ENTER to exit"): Input() CloseConsole()
EndIf</lang> Sample output:
123 : 123
12345 : 234
1234567 : 345
987654321 : 654
10001 : 000
-10001 : 000
-123 : 123
-100 : 100
100 : 100
-12345 : 234
1 : invalid input: too few digits
2 : invalid input: too few digits
-1 : invalid input: too few digits
-10 : invalid input: too few digits
2002 : invalid input: even number of digits
-2002 : invalid input: even number of digits
0 : invalid input: too few digits
Run BASIC
<lang runbasic>x$ = "123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0"
while word$(x$,i+1,",") <> ""
i = i + 1 a1$ = trim$(word$(x$,i,",")) if left$(a1$,1) = "-" then a$ = mid$(a1$,2) else a$ = a1$ if (len(a$) and 1) = 0 or len(a$) < 3 then print a1$;chr$(9);" length < 3 or is even" else print mid$(a$,((len(a$)-3)/2)+1,3);" ";a1$ end if
wend end</lang>
123 123 234 12345 345 1234567 654 987654321 000 10001 000 -10001 123 -123 100 -100 100 100 234 -12345 1 length < 3 or is even 2 length < 3 or is even -1 length < 3 or is even -10 length < 3 or is even 2002 length < 3 or is even -2002 length < 3 or is even 0 length < 3 or is even
Bracmat
<lang bracmat>( ( middle3
= x p
. @(!arg:? [?p:? [(1/2*!p+-3/2) %?x [(1/2*!p+3/2) ?)
& !x
| !arg
( !p:<3&"is too small"
| "has even number of digits"
)
)
& 123 12345 1234567 987654321 10001 -10001 -123 -100 100
-12345 1 2 -1 -10 2002 -2002 0 : ?L
& whl'(!L:%?e ?L&out$(middle3$!e)) & ); </lang> Output:
123 234 345 654 000 000 123 100 100 234 1 is too small 2 is too small -1 is too small -10 is too small 2002 has even number of digits -2002 has even number of digits 0 is too small
C
This code is followed by its output. <lang c>
- include <stdio.h>
- include <stdlib.h>
- include <string.h>
// we return a static buffer; caller wants it, caller copies it char * mid3(int n) { static char buf[32]; int l; sprintf(buf, "%d", n > 0 ? n : -n); l = strlen(buf); if (l < 3 || !(l & 1)) return 0; l = l / 2 - 1; buf[l + 3] = 0; return buf + l; }
int main(void) { int x[] = {123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0, 1234567890};
int i; char *m; for (i = 0; i < sizeof(x)/sizeof(x[0]); i++) { if (!(m = mid3(x[i]))) m = "error"; printf("%d: %s\n", x[i], m); } return 0; }</lang>
123: 123 12345: 234 1234567: 345 987654321: 654 10001: 000 -10001: 000 -123: 123 -100: 100 100: 100 -12345: 234 1: error 2: error -1: error -10: error 2002: error -2002: error 0: error 1234567890: error
Alternative Version
This code has been extensively rewritten. The original was purely interactive and had to be invoked each time from the console. It also did not produce the correct answer. <lang c>
- include <stdio.h>
- include <stdlib.h>
- include <string.h>
void midThree(char arg[]) {
char output[4];
int midPoint;
arg[0]=='-'?midPoint = ((strlen(arg) + 1) / 2):midPoint = ((strlen(arg) + 1) / 2) - 1;
if(strlen(arg) < 3)
{
printf("Error, %d is too short.\n",atoi(arg));
return ;
}
else if(strlen(arg) == 4 || strlen(arg) == 3)
{
printf("Error, %d has %d digits, no 3 middle digits.\n",atoi(arg),arg[0]=='-'?strlen(arg)-1:strlen(arg));
return ;
}
else{
for(int i=0; i<3; i++)
{
output[i] = arg[(midPoint-1) + i];
}
output[3] = '\0';
printf("The middle three digits of %s are %s.\n",arg,output);
}}
int main(int argc, char * argv[]) {
char input[50];
int x[] = {123, 12345, 1234567, 987654321, 10001, -10001,
-123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0, 1234567890},i;
if(argc < 2)
{
printf("Usage: %s <integer>\n",argv[0]);
printf("Examples with preloaded data shown below :\n");
for(i=0;i<18;i++)
{
midThree(itoa(x[i],argv[0],10)); }
return 1;
}
else
{
sprintf(input,"%d",atoi(argv[1]));
midThree(argv[1]);
return 0;
}
}</lang>
- Output:
Usage: C:\TurboC++\Disk\TurboC3\BIN\rosmid3_2.exe <integer> Examples with preloaded data shown below : Error, 123 has 3 digits, no 3 middle digits. The middle three digits of 12345 are 234. The middle three digits of 1234567 are 345. The middle three digits of 987654321 are 654. The middle three digits of 10001 are 000. The middle three digits of -10001 are 000. Error, -123 has 3 digits, no 3 middle digits. Error, -100 has 3 digits, no 3 middle digits. Error, 100 has 3 digits, no 3 middle digits. The middle three digits of -12345 are 234. Error, 1 is too short. Error, 2 is too short. Error, -1 is too short. Error, -10 has 2 digits, no 3 middle digits. Error, 2002 has 4 digits, no 3 middle digits. Error, -2002 has 4 digits, no 3 middle digits. Error, 0 is too short. The middle three digits of 1234567890 are 456.
C_sharp
<lang csharp>using System;
namespace RosettaCode {
class Program
{
static void Main(string[] args)
{
string text = Math.Abs(int.Parse(Console.ReadLine())).ToString();
Console.WriteLine(text.Length < 2 || text.Length % 2 == 0 ? "Error" : text.Substring((text.Length - 3) / 2, 3));
}
}
}</lang>
- Output:
123:123 12345:234 1234567:345 987654321:654 10001:000 -10001:000 -123:123 -100:100 100:100 -12345:234 1:Error 2:Error -1:Error -10:Error 2002:Error -2002:Error 0:Error
C++
<lang cpp>#include <iostream>
std::string middleThreeDigits(int n) {
auto number = std::to_string(std::abs(n)); auto length = number.size();
if (length < 3) {
return "less than three digits";
} else if (length % 2 == 0) {
return "even number of digits";
} else {
return number.substr(length / 2 - 1, 3);
}
}
int main() {
auto values {123, 12345, 1234567, 987654321, 10001,
-10001, -123, -100, 100, -12345,
1, 2, -1, -10, 2002, -2002, 0};
for (auto&& v : values) {
std::cout << "middleThreeDigits(" << v << "): " <<
middleThreeDigits(v) << "\n";
}
} </lang>
- Output:
middleThreeDigits(123): 123 middleThreeDigits(12345): 234 middleThreeDigits(1234567): 345 middleThreeDigits(987654321): 654 middleThreeDigits(10001): 000 middleThreeDigits(-10001): 000 middleThreeDigits(-123): 123 middleThreeDigits(-100): 100 middleThreeDigits(100): 100 middleThreeDigits(-12345): 234 middleThreeDigits(1): less than three digits middleThreeDigits(2): less than three digits middleThreeDigits(-1): less than three digits middleThreeDigits(-10): less than three digits middleThreeDigits(2002): even number of digits middleThreeDigits(-2002): even number of digits middleThreeDigits(0): less than three digits
Clojure
<lang Clojure> (defn middle3 [v]
(let [no (Math/abs v)
digits (str no)
len (count digits)]
(cond
(< len 3) :too_short
(even? len) :no_middle_in_even_no_of_digits
:else (let [mid (/ len 2)
start (- mid 2)]
(apply str
(take 3
(nthnext digits start)))))))
(def passes '(123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345)) (def fails '(1 2 -1 -10 2002 -2002 0))
</lang>
- Output:
user=> (map middle3 passes)
("123" "234" "345" "654" "000" "000" "123" "100" "100" "234")
user=> (map middle3 fails)
(:too_short :too_short :too_short :too_short :no_middle_in_even_no_of_digits :no_middle_in_even_no_of_digits :too_short)
COBOL
<lang COBOL>identification division. program-id. middle3. environment division. data division. working-storage section. 01 num pic 9(9).
88 num-too-small values are -99 thru 99.
01 num-disp pic ---------9.
01 div pic 9(9). 01 mod pic 9(9). 01 mod-disp pic 9(3).
01 digit-counter pic 999. 01 digit-div pic 9(9).
88 no-more-digits value 0.
01 digit-mod pic 9(9).
88 is-even value 0.
01 multiplier pic 9(9).
01 value-items.
05 filler pic s9(9) value 123. 05 filler pic s9(9) value 12345. 05 filler pic s9(9) value 1234567. 05 filler pic s9(9) value 987654321. 05 filler pic s9(9) value 10001. 05 filler pic s9(9) value -10001. 05 filler pic s9(9) value -123. 05 filler pic s9(9) value -100. 05 filler pic s9(9) value 100. 05 filler pic s9(9) value -12345. 05 filler pic s9(9) value 1. 05 filler pic s9(9) value 2. 05 filler pic s9(9) value -1. 05 filler pic s9(9) value -10. 05 filler pic s9(9) value 2002. 05 filler pic s9(9) value -2002. 05 filler pic s9(9) value 0.
01 value-array redefines value-items.
05 items pic s9(9) occurs 17 times indexed by item.
01 result pic x(20).
procedure division. 10-main.
perform with test after varying item from 1 by 1 until items(item) = 0
move items(item) to num
move items(item) to num-disp
perform 20-check
display num-disp " --> " result
end-perform.
stop run.
20-check.
if num-too-small
move "Number too small" to result
exit paragraph
end-if.
perform 30-count-digits.
divide digit-counter by 2 giving digit-div remainder digit-mod.
if is-even
move "Even number of digits" to result
exit paragraph
end-if.
*> if digit-counter is 5, mul by 10
*> if digit-counter is 7, mul by 100
*> if digit-counter is 9, mul by 1000
if digit-counter > 3
compute multiplier rounded = 10 ** (((digit-counter - 5) / 2) + 1)
divide num by multiplier giving num
divide num by 1000 giving div remainder mod
move mod to mod-disp
else
move num to mod-disp
end-if.
move mod-disp to result.
exit paragraph.
30-count-digits.
move zeroes to digit-counter.
move num to digit-div.
perform with test before until no-more-digits
divide digit-div by 10 giving digit-div remainder digit-mod
add 1 to digit-counter
end-perform.
exit paragraph.</lang>
Output
123 --> 123
12345 --> 234
1234567 --> 345
987654321 --> 654
10001 --> 000
-10001 --> 000
-123 --> 123
-100 --> 100
100 --> 100
-12345 --> 234
1 --> Number too small
2 --> Number too small
-1 --> Number too small
-10 --> Number too small
2002 --> Even number of digit
-2002 --> Even number of digit
0 --> Number too small
Optimised version <lang cobol>identification division. program-id. middle3. environment division. data division. working-storage section. 01 value-items.
05 filler pic s9(9) value 123.
05 filler pic s9(9) value 12345.
05 filler pic s9(9) value 1234567.
05 filler pic s9(9) value 987654321.
05 filler pic s9(9) value 10001.
05 filler pic s9(9) value -10001.
05 filler pic s9(9) value -123.
05 filler pic s9(9) value -100.
05 filler pic s9(9) value 100.
05 filler pic s9(9) value -12345.
05 filler pic s9(9) value 1.
05 filler pic s9(9) value 2.
05 filler pic s9(9) value -1.
05 filler pic s9(9) value -10.
05 filler pic s9(9) value 2002.
05 filler pic s9(9) value -2002.
05 filler pic s9(9) value 0.
01 value-array redefines value-items.
05 items pic s9(9) occurs 17 times indexed by item.
01 num pic 9(9). 01 num-disp pic ---------9. 01 num2 pic 9(9).
01 power pic 9. 01 power10 pic 9(16).
01 three-digits pic 999.
01 result pic X(20).
01 flag pic 9.
88 done value 1.
procedure division. 01-setup.
perform 02-outer with test after varying item from 1 by 1 until items(item) = 0. stop run.
02-outer.
move items(item) to num.
move items(item) to num-disp.
if num less than 100
move "too small" to result
else
perform 03-inner with test after varying power from 9 by -1 until power = 1 or done
end-if.
display num-disp " --> " result.
exit paragraph.
03-inner.
move 0 to flag.
compute power10 = 10 ** power.
if num >= power10
move 1 to flag
if function mod(power,2) = 1
move "even number digits" to result
else
move num to num2
compute num2 = num2 / ( 10 ** (( power / 2 ) - 1 ))
move function mod(num2,1000) to three-digits
move three-digits to result
end-if
end-if.
</lang> Output
123 --> 123
12345 --> 234
1234567 --> 345
987654321 --> 654
10001 --> 000
-10001 --> 000
-123 --> 123
-100 --> 100
100 --> 100
-12345 --> 234
1 --> too small
2 --> too small
-1 --> too small
-10 --> too small
2002 --> even number digits
-2002 --> even number digits
0 --> too small
Common Lisp
<lang lisp> (defun mid3 (n)
(let ((a (abs n))
(hmd)) ; how many digits
(labels ((give (fmt &optional x y) (return-from mid3 (format nil fmt x y)))
(need (x) (give "Need ~a digits, not ~d." x hmd))
(nbr (n) (give "~3,'0d" n)))
(when (zerop n) (give "Zero is 1 digit"))
(setq hmd (truncate (1+ (log a 10))))
(cond ((< hmd 3) (need "3+"))
((= hmd 3) (nbr a))
((evenp hmd) (need "odd number of"))
(t (nbr (mod (truncate a (expt 10 (/ (- hmd 3) 2))) 1000)))))))
</lang>
Test code:
<lang lisp> (loop as n in '(123 12345 1234567 987654321
10001 -10001 -123 -100 100 -12345
1 2 -1 -10 2002 -2002 0)
do (format t "~d:~12t~a~%" n (mid3 n)))
</lang>
- Output:
123: 123 12345: 234 1234567: 345 987654321: 654 10001: 000 -10001: 000 -123: 123 -100: 100 100: 100 -12345: 234 1: Need 3+ digits, not 1. 2: Need 3+ digits, not 1. -1: Need 3+ digits, not 1. -10: Need 3+ digits, not 2. 2002: Need odd number of digits, not 4. -2002: Need odd number of digits, not 4. 0: Zero is 1 digit
D
<lang d>import std.stdio, std.traits, std.conv;
string middleThreeDigits(T)(in T n) pure nothrow if (isIntegral!T) {
auto s = n < 0 ? n.text[1 .. $] : n.text;
auto len = s.length;
if (len < 3 || len % 2 == 0)
return "Need odd and >= 3 digits";
auto mid = len / 2;
return s[mid - 1 .. mid + 2];
}
void main() {
immutable passing = [123, 12345, 1234567, 987654321, 10001, -10001,
-123, -100, 100, -12345, long.min, long.max];
foreach (immutable n; passing)
writefln("middleThreeDigits(%s): %s", n, middleThreeDigits(n));
immutable failing = [1, 2, -1, -10, 2002, -2002, 0,int.min,int.max];
foreach (immutable n; failing)
writefln("middleThreeDigits(%s): %s", n, middleThreeDigits(n));
}</lang>
- Output:
middleThreeDigits(123): 123 middleThreeDigits(12345): 234 middleThreeDigits(1234567): 345 middleThreeDigits(987654321): 654 middleThreeDigits(10001): 000 middleThreeDigits(-10001): 000 middleThreeDigits(-123): 123 middleThreeDigits(-100): 100 middleThreeDigits(100): 100 middleThreeDigits(-12345): 234 middleThreeDigits(-9223372036854775808): 368 middleThreeDigits(9223372036854775807): 368 middleThreeDigits(1): Need odd and >= 3 digits middleThreeDigits(2): Need odd and >= 3 digits middleThreeDigits(-1): Need odd and >= 3 digits middleThreeDigits(-10): Need odd and >= 3 digits middleThreeDigits(2002): Need odd and >= 3 digits middleThreeDigits(-2002): Need odd and >= 3 digits middleThreeDigits(0): Need odd and >= 3 digits middleThreeDigits(-2147483648): Need odd and >= 3 digits middleThreeDigits(2147483647): Need odd and >= 3 digits
Alternative Version
This longer version gives a stronger typed output, and it tries to be faster avoiding conversions to string. <lang d>import std.stdio, std.traits, std.math, std.variant;
/// Returns a string with the error, or the three digits. Algebraic!(string, char[3]) middleThreeDigits(T)(in T n) if (isIntegral!T) {
// Awkward code to face abs(T.min) when T is signed.
ulong ln;
static if (isSigned!T) {
if (n >= 0) {
ln = n;
} else {
if (n == T.min) {
ln = -(n + 1);
ln++;
} else {
ln = -n;
}
}
} else {
ln = n;
}
if (ln < 100)
return typeof(return)("n is too short.");
immutable uint digits = 1 + cast(uint)log10(ln);
if (digits % 2 == 0)
return typeof(return)("n must have an odd number of digits.");
// From the Reddit answer by "millstone".
int drop = (digits - 3) / 2;
while (drop-- > 0)
ln /= 10;
char[3] result = void; result[2] = ln % 10 + '0'; ln /= 10; result[1] = ln % 10 + '0'; ln /= 10; result[0] = ln % 10 + '0'; return typeof(return)(result);
}
void main() {
immutable passing = [123, 12345, 1234567, 987654321, 10001,
-10001, -123, -100, 100, -12345, -8765432];
foreach (n; passing) {
auto mtd = middleThreeDigits(n);
// A string result means it didn't pass.
assert(!mtd.peek!string);
writefln("middleThreeDigits(%d): %s", n, mtd);
}
writeln();
immutable failing = [1, 2, -1, -10, 2002, -2002, 0,
15, int.min, int.max];
foreach (n; failing) {
auto mtd = middleThreeDigits(n);
assert(mtd.peek!string);
writefln("middleThreeDigits(%d): %s", n, mtd);
}
writeln();
immutable long[] passingL = [123, 12345, 1234567, 987654321, 10001,
-10001, -123, -100, 100, -12345,
-8765432, long.min, long.max];
foreach (n; passingL) {
auto mtd = middleThreeDigits(n);
assert(!mtd.peek!string);
writefln("middleThreeDigits(%d): %s", n, mtd);
}
writeln();
immutable long[] failingL = [1, 2, -1, -10, 2002, -2002, 0, 15];
foreach (n; failingL) {
auto mtd = middleThreeDigits(n);
assert(mtd.peek!string);
writefln("middleThreeDigits(%d): %s", n, mtd);
}
writeln();
{
immutable n = short.min;
auto mtd = middleThreeDigits(n);
assert(!mtd.peek!string);
writefln("middleThreeDigits(cast(short)%d): %s", n, mtd);
}
}</lang>
- Output:
middleThreeDigits(123): 123 middleThreeDigits(12345): 234 middleThreeDigits(1234567): 345 middleThreeDigits(987654321): 654 middleThreeDigits(10001): 000 middleThreeDigits(-10001): 000 middleThreeDigits(-123): 123 middleThreeDigits(-100): 100 middleThreeDigits(100): 100 middleThreeDigits(-12345): 234 middleThreeDigits(-8765432): 654 middleThreeDigits(1): n is too short. middleThreeDigits(2): n is too short. middleThreeDigits(-1): n is too short. middleThreeDigits(-10): n is too short. middleThreeDigits(2002): n must have an odd number of digits. middleThreeDigits(-2002): n must have an odd number of digits. middleThreeDigits(0): n is too short. middleThreeDigits(15): n is too short. middleThreeDigits(-2147483648): n must have an odd number of digits. middleThreeDigits(2147483647): n must have an odd number of digits. middleThreeDigits(123): 123 middleThreeDigits(12345): 234 middleThreeDigits(1234567): 345 middleThreeDigits(987654321): 654 middleThreeDigits(10001): 000 middleThreeDigits(-10001): 000 middleThreeDigits(-123): 123 middleThreeDigits(-100): 100 middleThreeDigits(100): 100 middleThreeDigits(-12345): 234 middleThreeDigits(-8765432): 654 middleThreeDigits(-9223372036854775808): 368 middleThreeDigits(9223372036854775807): 368 middleThreeDigits(1): n is too short. middleThreeDigits(2): n is too short. middleThreeDigits(-1): n is too short. middleThreeDigits(-10): n is too short. middleThreeDigits(2002): n must have an odd number of digits. middleThreeDigits(-2002): n must have an odd number of digits. middleThreeDigits(0): n is too short. middleThreeDigits(15): n is too short. middleThreeDigits(cast(short)-32768): 276
Eiffel
<lang Eiffel> class APPLICATION
create make
feature
make -- Test of middle_three_digits. do test_1 := <<123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345>> test_2 := <<1, 2, -1, -10, 2002, -2002, 0>> across test_1 as t loop io.put_string ("The middle three digits of " + t.item.out + " are: %T ") io.put_string (middle_three_digits (t.item) + "%N") end across test_2 as t loop io.put_string ("The middle three digits of " + t.item.out + " are: %T") io.put_string (middle_three_digits (t.item) + "%N") end end
test_1, test_2: ARRAY [INTEGER]
middle_three_digits (n: INTEGER): STRING -- The middle three digits of 'n'. local k: INTEGER i: REAL_64 in: STRING do create in.make_empty in := n.out if n < 0 then in.prune ('-') end create Result.make_empty if in.count < 3 then io.put_string (" Not enough digits. ") elseif in.count \\ 2 = 0 then io.put_string (" Even number of digits. ") else i := (in.count - 3) / 2 from k := i.floor + 1 until k > i + 3 loop Result.extend (in.at (k)) k := k + 1 end end end
end </lang>
- Output:
The middle three digits of 123 are: 123 The middle three digits of 12345 are: 234 The middle three digits of 1234567 are: 345 The middle three digits of 987654321 are: 654 The middle three digits of 10001 are: 000 The middle three digits of -10001 are: 000 The middle three digits of -123 are: 123 The middle three digits of -100 are: 100 The middle three digits of 100 are: 100 The middle three digits of -12345 are: 234 The middle three digits of 1 are: Not enough digits. The middle three digits of 2 are: Not enough digits. The middle three digits of -1 are: Not enough digits. The middle three digits of -10 are: Not enough digits. The middle three digits of 2002 are: Even number of digits. The middle three digits of -2002 are: Even number of digits. The middle three digits of 0 are: Not enough digits.
Erlang
<lang erlang>% -module(middle_three_digits). -export([main/0]).
main() -> digits(123), digits(12345), digits(1234567), digits(987654321), digits(10001), digits(-10001), digits(-123), digits(-100), digits(100), digits(-12345), digits(1), digits(2), digits(-1), digits(-10), digits(2002), digits(-2002), digits(0).
digits(N) when N < 0 -> digits(-N); digits(N) when (N div 100) =:= 0 -> io:format("too small\n"); digits(N) -> K=length(integer_to_list(N)), if (K rem 2) =:= 0 -> io:format("even number of digits\n"); true -> loop((K-3) div 2 , N) end.
loop(0, N) -> io:format("~3..0B~n",[N rem 1000]); loop(X,N) when X>0 -> loop(X-1, N div 10). </lang>
- Output:
123 234 345 654 000 000 123 100 100 234 too small too small too small too small even number of digits even number of digits too small ok
Forth
This is a problem, which is easily solved in Forth. It converts the number to a string and checks it length. If the number does not represent a printable string, it returns an empty string. <lang forth>: middle3 ( n1 -- a n2)
abs s>d <# #s #> dup 2/ 0<> over 1 and 0<> and if 2/ 1- chars + 3 else drop 0 then
- </lang>
Fortran
Please find compilation instructions along with the output for the examples in the comments at the beginning of the file. This program was produced in an Ubuntu distribution of the GNU/linux system. <lang FORTRAN> !-*- mode: compilation; default-directory: "/tmp/" -*- !Compilation started at Sat Jun 1 14:48:41 ! !a=./f && make $a && OMP_NUM_THREADS=2 $a < unixdict.txt # some of the compilation options and redirection from unixdict.txt are vestigial. !gfortran -std=f2008 -Wall -fopenmp -ffree-form -fall-intrinsics -fimplicit-none f.f08 -o f ! 123 123 ! 12345 234 ! 1234567 345 ! 987654321 654 ! 10001 000 ! -10001 000 ! -123 123 ! -100 100 ! 100 100 ! -12345 234 ! 1 Too short ! 2 Too short ! -1 Too short ! -10 Too short ! 2002 Digit count too even ! -2002 Digit count too even ! 0 Too short ! !Compilation finished at Sat Jun 1 14:48:41
program MiddleMuddle
integer, dimension(17) :: itest, idigits integer :: i, n data itest/123,12345,1234567,987654321,10001,-10001,-123,-100,100,-12345,1,2,-1,-10,2002,-2002,0/ do i = 1, size(itest) call antibase(10, abs(itest(i)), idigits, n) write(6,'(i20,2x,a20)') itest(i), classifym3(idigits, n) if (0 .eq. itest(i)) exit end do
contains
logical function even(n) integer, intent(in) :: n even = 0 .eq. iand(n,1) end function even
function classifym3(iarray, n) result(s)
integer, dimension(:), intent(in) :: iarray
integer, intent(in) :: n
character(len=20) :: s
integer :: i,m
if (n < 3) then
s = 'Too short'
else if (even(n)) then
s = 'Digit count too even'
else
m = (n+1)/2
write(s,'(3i1)')(iarray(i), i=m+1,m-1,-1)
end if
end function classifym3
subroutine antibase(base, m, digits, n) ! digits ordered by increasing significance
integer, intent(in) :: base, m
integer, intent(out) :: n ! the number of digits
integer, dimension(:), intent(out) :: digits
integer :: em
em = m
do n=1, size(digits)
digits(n) = mod(em, base)
em = em / base
if (0 .eq. em) return
end do
stop 'antibase ran out of space to store result'
end subroutine antibase
end program MiddleMuddle </lang>
Go
Unlike most Go examples on RC, this is written as a package to show operation of the go test tool.
File m3.go: <lang go>package m3
import (
"errors" "strconv"
)
var (
ErrorLT3 = errors.New("N of at least three digits required.")
ErrorEven = errors.New("N with odd number of digits required.")
)
func Digits(i int) (string, error) {
if i < 0 {
i = -i
}
if i < 100 {
return "", ErrorLT3
}
s := strconv.Itoa(i)
if len(s)%2 == 0 {
return "", ErrorEven
}
m := len(s) / 2
return s[m-1 : m+2], nil
}</lang> File m3_test.go: <lang go>package m3_test
import (
"testing"
"m3"
)
func TestPassing(t *testing.T) {
type s struct {
i int
m string
}
tcs := []s{
{123, "123"},
{12345, "234"},
{1234567, "345"},
{987654321, "654"},
{10001, "000"},
{-10001, "000"},
}
for _, tc := range tcs {
m, err := m3.Digits(tc.i)
if err != nil {
t.Fatalf("d(%d) returned %q.", tc.i, err)
}
if m != tc.m {
t.Fatalf("d(%d) expected %q, got %q.", tc.i, tc.m, m)
}
t.Logf("d(%d) = %q.", tc.i, m)
}
}
func TestFailing(t *testing.T) {
type s struct {
i int
err error
}
tcs := []s{
{1, m3.ErrorLT3},
{2, m3.ErrorLT3},
{-1, m3.ErrorLT3},
{-10, m3.ErrorLT3},
{2002, m3.ErrorEven},
{-2002, m3.ErrorEven},
{0, m3.ErrorLT3},
}
for _, tc := range tcs {
m, err := m3.Digits(tc.i)
if err == nil {
t.Fatal("d(%d) expected error %q, got non-error %q.",
tc.i, tc.err, m)
}
if err != tc.err {
t.Fatal("d(d) expected error %q, got %q", tc.i, tc.err, err)
}
t.Logf("d(%d) returns %q", tc.i, err)
}
}</lang>
- Output:
Output of go test is normally terse:
> go test PASS ok m3 0.008s
With -v (for verbose):
> go test -v
=== RUN TestPassing-4
--- PASS: TestPassing-4 (0.00 seconds)
m3_test.go:30: d(123) = "123".
m3_test.go:30: d(12345) = "234".
m3_test.go:30: d(1234567) = "345".
m3_test.go:30: d(987654321) = "654".
m3_test.go:30: d(10001) = "000".
m3_test.go:30: d(-10001) = "000".
=== RUN TestFailing-4
--- PASS: TestFailing-4 (0.00 seconds)
m3_test.go:57: d(1) returns "N of at least three digits required."
m3_test.go:57: d(2) returns "N of at least three digits required."
m3_test.go:57: d(-1) returns "N of at least three digits required."
m3_test.go:57: d(-10) returns "N of at least three digits required."
m3_test.go:57: d(2002) returns "N with odd number of digits required."
m3_test.go:57: d(-2002) returns "N with odd number of digits required."
m3_test.go:57: d(0) returns "N of at least three digits required."
PASS
ok m3 0.008s
Groovy
<lang groovy>def middleThree(Number number) {
def text = Math.abs(number) as String assert text.size() >= 3 : "'$number' must be more than 3 numeric digits" assert text.size() % 2 == 1 : "'$number' must have an odd number of digits"
int start = text.size() / 2 - 1 text[start..(start+2)]
}</lang> Test Code: <lang groovy>[123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0].each { number ->
def text = (number as String).padLeft(10)
try {
println "$text: ${middleThree(number)}"
} catch(AssertionError error) {
println "$text cannot be converted: $error.message"
}
}</lang> Output:
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1 cannot be converted: '1' must be more than 3 numeric digits. Expression: (text.size() >= 3)
2 cannot be converted: '2' must be more than 3 numeric digits. Expression: (text.size() >= 3)
-1 cannot be converted: '-1' must be more than 3 numeric digits. Expression: (text.size() >= 3)
-10 cannot be converted: '-10' must be more than 3 numeric digits. Expression: (text.size() >= 3)
2002 cannot be converted: '2002' must have an odd number of digits. Expression: ((text.size() % 2) == 1)
-2002 cannot be converted: '-2002' must have an odd number of digits. Expression: ((text.size() % 2) == 1)
0 cannot be converted: '0' must be more than 3 numeric digits. Expression: (text.size() >= 3)
Haskell
<lang haskell>import Numeric
mid3 :: Integral a => a -> Either String String mid3 n | m < 100 = Left "is too small"
| even l = Left "has an even number of digits"
| otherwise = Right . take 3 $ drop ((l-3) `div` 2) s
where m = abs n
s = showInt m ""
l = length s
showMid3 :: Integer -> String showMid3 n = show n ++ ": " ++ either id id (mid3 n)
main :: IO () main = mapM_ (putStrLn . showMid3) [
123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0]</lang>
Output:
123: 123 12345: 234 1234567: 345 987654321: 654 10001: 000 -10001: 000 -123: 123 -100: 100 100: 100 -12345: 234 1: is too small 2: is too small -1: is too small -10: is too small 2002: has an even number of digits -2002: has an even number of digits 0: is too small
Icon and Unicon
The following solution works in both languages.
<lang unicon>procedure main(a)
every n := !a do write(right(n,15)," -> ",midM(n))
end
procedure midM(n,m)
/m := 3
n := abs(n)
return n ? if (*n >= m) then
if (((*n-m) % 2) = 0) then (move((*n - m)/2),move(m))
else "wrong number of digits"
else "too short"
end</lang>
with output:
->m3d 123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1 -10 2002 -2002 0
123 -> 123
12345 -> 234
1234567 -> 345
987654321 -> 654
10001 -> 000
-10001 -> 000
-123 -> 123
-100 -> 100
100 -> 100
-12345 -> 234
1 -> too short
2 -> too short
-1 -> too short
-10 -> too short
2002 -> wrong number of digits
-2002 -> wrong number of digits
0 -> too short
->
J
Solution: <lang j>asString=: ":"0 NB. convert vals to strings getPfxSize=: [: -:@| 3 -~ # NB. get size of prefix to drop before the 3 middle digits getMid3=: (3 {. getPfxSize }. ,&'err') :: ('err'"_) NB. get 3 middle digits or return 'err' getMiddle3=: getMid3@asString@:|</lang> Example: <lang j> vals=: 123 12345 1234567 987654321 10001 _10001 _123 _100 100 _12345 1 2 _1 _10 2002 _2002 0
getMiddle3 vals
123 234 345 654 000 000 123 100 100 234 err err err err err err err</lang>
Java
<lang Java>public class MiddleThreeDigits {
public static void main(String[] args) {
final long[] passing = {123, 12345, 1234567, 987654321, 10001, -10001,
-123, -100, 100, -12345, Long.MIN_VALUE, Long.MAX_VALUE};
final int[] failing = {1, 2, -1, -10, 2002, -2002, 0, Integer.MIN_VALUE,
Integer.MAX_VALUE};
for (long n : passing)
System.out.printf("middleThreeDigits(%s): %s\n", n, middleThreeDigits(n));
for (int n : failing)
System.out.printf("middleThreeDigits(%s): %s\n", n, middleThreeDigits(n));
}
public static <T> String middleThreeDigits(T n) {
String s = String.valueOf(n);
if (s.charAt(0) == '-')
s = s.substring(1);
int len = s.length();
if (len < 3 || len % 2 == 0)
return "Need odd and >= 3 digits";
int mid = len / 2;
return s.substring(mid - 1, mid + 2);
}
}</lang>
middleThreeDigits(123): 123 middleThreeDigits(12345): 234 middleThreeDigits(1234567): 345 middleThreeDigits(987654321): 654 middleThreeDigits(10001): 000 middleThreeDigits(-10001): 000 middleThreeDigits(-123): 123 middleThreeDigits(-100): 100 middleThreeDigits(100): 100 middleThreeDigits(-12345): 234 middleThreeDigits(-9223372036854775808): 368 middleThreeDigits(9223372036854775807): 368 middleThreeDigits(1): Need odd and >= 3 digits middleThreeDigits(2): Need odd and >= 3 digits middleThreeDigits(-1): Need odd and >= 3 digits middleThreeDigits(-10): Need odd and >= 3 digits middleThreeDigits(2002): Need odd and >= 3 digits middleThreeDigits(-2002): Need odd and >= 3 digits middleThreeDigits(0): Need odd and >= 3 digits middleThreeDigits(-2147483648): Need odd and >= 3 digits middleThreeDigits(2147483647): Need odd and >= 3 digits
JavaScript
<lang JavaScript>function middleThree(x){
var n=+Math.abs(x); var l=n.length-1; if(l<2||l%2) throw new Error(x+': Invalid length '+(l+1)); return n.slice(l/2-1,l/2+2);
}
[123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0].forEach(function(n){
try{console.log(n,middleThree(n))}catch(e){console.error(e.message)}
});</lang>
123 "123" 12345 "234" 1234567 "345" 987654321 "654" 10001 "000" -10001 "000" -123 "123" -100 "100" 100 "100" -12345 "234" 1: Invalid length 1 2: Invalid length 1 -1: Invalid length 1 -10: Invalid length 2 2002: Invalid length 4 -2002: Invalid length 4 0: Invalid length 1
jq
<lang jq>def middle3:
if . < 0 then -. else . end | tostring as $s | ($s | length) as $n | if $n<3 or ($n % 2) == 0 then "invalid length: \($n)" else (($n - 1) / 2) as $n | $s[$n - 1 : $n + 2] end ;
(123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0)
| "\(.) => \( .|middle3 )"</lang>
Typescript:<lang sh> $ jq -r -n -f Middle_three_digits.jq 123 => 123 12345 => 234 1234567 => 345 987654321 => 654 10001 => 000 -10001 => 000 -123 => 123 -100 => 100 100 => 100 -12345 => 234 1 => invalid length: 1 2 => invalid length: 1 -1 => invalid length: 1 -10 => invalid length: 2 2002 => invalid length: 4 -2002 => invalid length: 4 0 => invalid length: 1 </lang>
Julia
<lang julia>function middle(i)
s = string(abs(i))
l = length(s)
mid = int((l+1)/2)
l < 3 ?
"error: not enough digits" :
iseven(l) ?
"error: number of digits is even" :
join((s[mid-1],s[mid],s[mid+1]))
end
function dummy(x,y,z=5)
"""
A dummy docstring over two lines
for text coloration.
"""
print("this is just some text to show text", 1.0, 3)
# and comment coloration
// and comment coloration 2
end
julia>
for n = [123, 12345, 1234567, 987654321, 10001, -10001, -123,
-100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0]
println (@sprintf("%10d : ", n), middle(n))
end</lang>
Output
123 : 123
12345 : 234
1234567 : 345
987654321 : 654
10001 : 000
-10001 : 000
-123 : 123
-100 : 100
100 : 100
-12345 : 234
1 : error: not enough digits
2 : error: not enough digits
-1 : error: not enough digits
-10 : error: not enough digits
2002 : error: number of digits is even
-2002 : error: number of digits is even
0 : error: not enough digits
Lasso
<lang Lasso>define middlethree(value::integer) => { local( pos_value = math_abs(#value), stringvalue = #pos_value -> asstring, intlength = #stringvalue -> size, middle = integer((#intlength + 1) / 2), prefix = string(#value) -> padleading(15)& + ': ' )
#intlength < 3 ? return #prefix + 'Error: too few digits' not(#intlength % 2) ? return #prefix + 'Error: even number of digits'
return #prefix + #stringvalue -> sub(#middle -1, 3)
}
'
'
with number in array(123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0) do {^
middlethree(#number)
'<br />'
^}
''</lang>
Output
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1: Error: too few digits
2: Error: too few digits
-1: Error: too few digits
-10: Error: too few digits
2002: Error: even number of digits
-2002: Error: even number of digits
0: Error: too few digits
Lua
<lang lua>function middle_three(n) if n < 0 then n = -n end
n = tostring(n) if #n % 2 == 0 then return "Error: the number of digits is even." elseif #n < 3 then return "Error: the number has less than 3 digits." end
local l = math.floor(#n/2) return n:sub(l, l+2) end
-- test do local t = {123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0}
for _,n in pairs(t) do print(n, middle_three(n)) end end</lang>
- Output:
123 123 12345 234 1234567 345 987654321 654 10001 000 -10001 000 -123 123 -100 100 100 100 -12345 234 1 Error: the number has less than 3 digits. 2 Error: the number has less than 3 digits. -1 Error: the number has less than 3 digits. -10 Error: the number is even. 2002 Error: the number is even. -2002 Error: the number is even. 0 Error: the number has less than 3 digits.
Mathematica
<lang Mathematica>middleThree[n_Integer] :=
Block[{digits = IntegerDigits[n], len},
len = Length[digits];
If[len < 3 || EvenQ[len], "number digits odd or less than 3",
len = Ceiling[len/2];
StringJoin @@ (ToString /@ digitslen - 1 ;; len + 1)]]
testData = {123, 12345, 1234567, 987654321, 10001, -10001, -123, -100,
100, -12345, 1, 2, -1, -10, 2002, -2002, 0};
Column[middleThree /@ testData]</lang>
- Output:
123 234 345 654 000 000 123 100 100 234 err: n too small err: n too small err: n too small err: n too small err: even number of digits err: even number of digits err: n too small
MATLAB / Octave
<lang MATLAB>function s=middle_three_digits(a) % http://rosettacode.org/wiki/Middle_three_digits
s=num2str(abs(a));
if ~mod(length(s),2) s='*** error: number of digits must be odd ***'; return; end; if length(s)<3, s='*** error: number of digits must not be smaller than 3 ***'; return; end;
s = s((length(s)+1)/2+[-1:1]);</lang> Test with <lang MATLAB> x=[123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0]; for k=1:length(x); fprintf(1,'%9i:%s\n',x(k),middle_three_digits(x(k)));end;</lang> Result
123:123
12345:234
1234567:457
987654321:654
10001:000
-10001:000
-123:123
-100:100
100:100
-12345:234
1:*** error: number of digits must not be smaller than 3 ***
2:*** error: number of digits must not be smaller than 3 ***
-1:*** error: number of digits must not be smaller than 3 ***
-10:*** error: number of digits must be odd ***
2002:*** error: number of digits must be odd ***
-2002:*** error: number of digits must be odd ***
0:*** error: number of digits must not be smaller than 3 ***
МК-61/52
<lang>П0 lg [x] 3 - x>=0 23 ИП0 1 0 / [x] ^ lg [x] 10^x П1 / {x} ИП1
- БП 00 1 + x=0 29 ИП0 С/П 0
/</lang>
Instruction: enter the number in the РX (on display), the result after the execution of the same. In the case of an even or less than 3 number of digits the indicator displays an error message.
ML
mLite
<lang ocaml> val test_array = ["123","12345","1234567","987654321","10001","~10001","~123","~100","100","~12345","1","2","~1","~10","2002","~2002","0"];
fun even (x rem 2 = 0) = true | _ = false;
fun middleThreeDigits (h :: t, s, 1 ) = s @ " --> too small" | (h :: t, s, 2 ) = s @ " --> has even digits" | (h :: t, s, 3 ) where (len (h :: t) = 3) = s @ " --> " @ (implode (h :: t)) | (h :: t, s, 3 ) = (middleThreeDigits ( sub (t, 0, (len t)-1), s, 3)) | (h :: t, s, m) = if len (h :: t) < 3 then middleThreeDigits (h :: t, s, 1) else if even ` len (h :: t) then middleThreeDigits (h :: t, s, 2) else middleThreeDigits (h :: t, s, 3)
| s = if sub (s, 0, 1) = "~" then
middleThreeDigits (sub (explode s, 1, len s), s, 0)
else
middleThreeDigits (explode s, s, 0)
;
map (println o middleThreeDigits) test_array;</lang> Output:
123 --> 123 12345 --> 234 1234567 --> 345 987654321 --> 654 10001 --> 000 ~10001 --> 000 ~123 --> 123 ~100 --> 100 100 --> 100 ~12345 --> 234 1 --> too small 2 --> too small ~1 --> too small ~10 --> too small 2002 --> has even digits ~2002 --> has even digits 0 --> too small
NetRexx
This sample goes the extra mile and provides a method that can display the middle N digits from the input value. To satisfy the requirements of this task, a static invocation of this general method is also provided with the value 3 hard coded as the digit count. <lang NetRexx>/* NetRexx */ options replace format comments java crossref symbols nobinary
sl = '123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345' -
'1 2 -1 -10 2002 -2002 0' -
'abc 1e3 -17e-3 4004.5 12345678 9876543210' -- extras
parse arg digsL digsR . if \digsL.datatype('w') then digsL = 3 if \digsR.datatype('w') then digsR = digsL if digsL > digsR then digsR = digsL
loop dc = digsL to digsR
say 'Middle' dc 'characters' loop nn = 1 to sl.words() val = sl.word(nn) say middleDigits(dc, val) end nn say end dc
return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method middle3Digits(val) constant
return middleDigits(3, val)
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ method middleDigits(digitCt, val) constant
text = val.right(15)':'
even = digitCt // 2 == 0 -- odd or even?
select
when digitCt <= 0 then text = 'digit selection size must be >= 1'
when \val.datatype('w') then text = text 'is not a whole number'
when val.abs().length < digitCt then text = text 'has less than' digitCt 'digits'
when \even & val.abs().length // 2 == 0 then text = text 'does not have an odd number of digits'
when even & val.abs().length // 2 \= 0 then text = text 'does not have an even number of digits'
otherwise do
val = val.abs()
valL = val.length
cutP = (valL - digitCt) % 2
text = text val.substr(cutP + 1, digitCt)
end
catch NumberFormatException
text = val 'is not numeric'
end
return text
</lang> Output:
Middle 3 characters
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1: has less than 3 digits
2: has less than 3 digits
-1: has less than 3 digits
-10: has less than 3 digits
2002: does not have an odd number of digits
-2002: does not have an odd number of digits
0: has less than 3 digits
abc: is not a whole number
1e3: is not a whole number
-17e-3: is not a whole number
4004.5: is not a whole number
12345678: does not have an odd number of digits
9876543210: does not have an odd number of digits
Nim
<lang nim>import math
proc middleThreeDigits(i): auto =
var s = $abs(i) if s.len < 3 or s.len mod 2 == 0: raise newException(ValueError, "Need odd and >= 3 digits") let mid = s.len div 2 return s[mid-1..mid+1]
const passing = @[123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345] const failing = @[1, 2, -1, -10, 2002, -2002, 0]
for i in passing & failing:
var answer = try: middleThreeDigits(i)
except ValueError: getCurrentExceptionMsg()
echo "middleThreeDigits(",i,") returned: ",answer</lang>
Output:
middleThreeDigits(123) returned: 123 middleThreeDigits(12345) returned: 234 middleThreeDigits(1234567) returned: 345 middleThreeDigits(987654321) returned: 654 middleThreeDigits(10001) returned: 000 middleThreeDigits(-10001) returned: 000 middleThreeDigits(-123) returned: 123 middleThreeDigits(-100) returned: 100 middleThreeDigits(100) returned: 100 middleThreeDigits(-12345) returned: 234 middleThreeDigits(1) returned: Need odd and >= 3 digits middleThreeDigits(2) returned: Need odd and >= 3 digits middleThreeDigits(-1) returned: Need odd and >= 3 digits middleThreeDigits(-10) returned: Need odd and >= 3 digits middleThreeDigits(2002) returned: Need odd and >= 3 digits middleThreeDigits(-2002) returned: Need odd and >= 3 digits middleThreeDigits(0) returned: Need odd and >= 3 digits
OCaml
<lang ocaml>let even x = (x land 1) <> 1
let middle_three_digits x =
let s = string_of_int (abs x) in let n = String.length s in if n < 3 then failwith "need >= 3 digits" else if even n then failwith "need odd number of digits" else String.sub s (n / 2 - 1) 3
let passing = [123; 12345; 1234567; 987654321; 10001; -10001; -123; -100; 100; -12345] let failing = [1; 2; -1; -10; 2002; -2002; 0]
let print x =
let res = try (middle_three_digits x) with Failure e -> "failure: " ^ e in Printf.printf "%d: %s\n" x res
let () =
print_endline "Should pass:"; List.iter print passing; print_endline "Should fail:"; List.iter print failing;
- </lang>
- Output:
Should pass: 123: 123 12345: 234 1234567: 345 987654321: 654 10001: 000 -10001: 000 -123: 123 -100: 100 100: 100 -12345: 234 Should fail: 1: failure: need >= 3 digits 2: failure: need >= 3 digits -1: failure: need >= 3 digits -10: failure: need >= 3 digits 2002: failure: need odd number of digits -2002: failure: need odd number of digits 0: failure: need >= 3 digits
Oforth
<lang Oforth>Integer method: middle3 { | s sz deb |
self abs asString dup ->s size ->sz sz 3 < ifTrue: [ "Too short" println return ] sz isEven ifTrue: [ "Not odd number of digits" println return ] sz 3 - 2 / 1 + ->deb s extract(deb, deb 2 +)
}</lang>
- Output:
[ 123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345] map(#middle3) println [123, 234, 345, 654, 000, 000, 123, 100, 100, 234] [ 1, 2, -1, -10, 2002, -2002, 0 ] apply(#middle3) Too short Too short Too short Too short Not odd number of digits Not odd number of digits Too short
PARI/GP
<lang parigp>middle(n)=my(v=digits(n));if(#v>2&&#v%2,100*v[#v\2]+10*v[#v\2+1]+v[#v\2+2],"no middle 3 digits"); apply(middle,[123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0])</lang> Output:
%1 = [123, 234, 345, 654, 0, 0, 123, 100, 100, 234, "no middle 3 digits", "no middle 3 digits", "no middle 3 digits", "no middle 3 digits", "no middle 3 digits", "no middle 3 digits", "no middle 3 digits"]
If for some reason you want to see the leading digits, you can run <lang parigp>apply(n-> Strprintf("%03d", n), %)</lang>
For earlier versions digits can be defined as
<lang parigp>digits(n)=eval(Vec(Str(n)))</lang>
or more efficiently as
<lang parigp>digits(n)=Vec(apply(n->n-48,Vectorsmall(Str(n))))</lang>
Perl
<lang Perl>#!/usr/bin/perl use strict ; use warnings ;
sub middlethree {
my $number = shift ;
my $testnumber = abs $number ;
my $error = "Middle 3 digits can't be shown" ;
my $numberlength = length $testnumber ;
if ( $numberlength < 3 ) {
print "$error : $number too short!\n" ;
return ;
}
if ( $numberlength % 2 == 0 ) {
print "$error : even number of digits in $number!\n" ;
return ;
}
my $middle = int ( $numberlength / 2 ) ;
print "Middle 3 digits of $number : " . substr( $testnumber , $middle - 1 , 3 ) . " !\n" ;
return ;
}
my @numbers = ( 123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345 ,
1, 2, -1, -10, 2002, -2002, 0 ) ;
map { middlethree( $_ ) } @numbers ; </lang>
- Output:
Middle 3 digits of 123 : 123 ! Middle 3 digits of 12345 : 234 ! Middle 3 digits of 1234567 : 345 ! Middle 3 digits of 987654321 : 654 ! Middle 3 digits of 10001 : 000 ! Middle 3 digits of -10001 : 000 ! Middle 3 digits of -123 : 123 ! Middle 3 digits of -100 : 100 ! Middle 3 digits of 100 : 100 ! Middle 3 digits of -12345 : 234 ! Middle 3 digits can't be shown : 1 too short! Middle 3 digits can't be shown : 2 too short! Middle 3 digits can't be shown : -1 too short! Middle 3 digits can't be shown : -10 too short! Middle 3 digits can't be shown : even number of digits in 2002! Middle 3 digits can't be shown : even number of digits in -2002! Middle 3 digits can't be shown : 0 too short!
Perl 6
<lang Perl6>sub middle-three($n) {
given $n.abs {
when .chars < 3 { "$n is too short" }
when .chars %% 2 { "$n has an even number of digits" }
default { "The three middle digits of $n are: ", .substr: (.chars - 3)/2, 3 }
}
}
say middle-three($_) for <
123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1 -10 2002 -2002 0
>;</lang>
- Output:
The three middle digits of 123 are: 123 The three middle digits of 12345 are: 234 The three middle digits of 1234567 are: 345 The three middle digits of 987654321 are: 654 The three middle digits of 10001 are: 000 The three middle digits of -10001 are: 000 The three middle digits of -123 are: 123 The three middle digits of -100 are: 100 The three middle digits of 100 are: 100 The three middle digits of -12345 are: 234 1 is too short 2 is too short -1 is too short -10 is too short 2002 has an even number of digits -2002 has an even number of digits 0 is too short
PHP
<lang PHP>// 32-bit builds of PHP: Integers can be from -2147483648 to 2147483647 // 64-bit builds of PHP: Integers can be from -9223372036854775808 to 9223372036854775807
function middlethree($integer) { $int = (int)str_replace('-',,$integer); $length = strlen($int);
if(is_int($int)) { if($length >= 3) { if($length % 2 == 1) { $middle = floor($length / 2) - 1; return substr($int,$middle, 3); } else { return 'The value must contain an odd amount of digits...'; } } else { return 'The value must contain at least three digits...'; } } else { return 'The value does not appear to be an integer...'; } }
$numbers = array(123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0);
foreach($numbers as $nums)
{
echo $nums.' : '.middlethree($nums). '
';
}</lang>
Output:
123 : 123 12345 : 234 1234567 : 345 987654321 : 654 10001 : 000 -10001 : 000 -123 : 123 -100 : 100 100 : 100 -12345 : 234 1 : The value must contain at least three digits... 2 : The value must contain at least three digits... -1 : The value must contain at least three digits... -10 : The value must contain at least three digits... 2002 : The value must contain an odd amount of digits... -2002 : The value must contain an odd amount of digits... 0 : The value must contain at least three digits...
PicoLisp
<lang PicoLisp>(de middle3digits (N)
(let (Lst (chop (abs N)) Len (length Lst))
(tab (10 -2 -30)
N
":"
(cond
((> 3 Len) "not enough digits")
((bit? 1 Len)
(head 3 (nth Lst (/ Len 2))) )
(T "even number of digits") ) ) ) )</lang>
Test: <lang PicoLisp>(mapc middle3digits
(123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345
1 2 -1 -10 2002 -2002 0 ) )</lang>
Output:
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1: not enough digits
2: not enough digits
-1: not enough digits
-10: not enough digits
2002: even number of digits
-2002: even number of digits
0: not enough digits
PL/I
<lang PL/I> middle: procedure options (main); /* 29 October 2013 */
declare n fixed (15); declare s character (25) varying; declare in file input;
open file (in) title ('/MIDDLE.DAT,type(text),recsize(100)');
on endfile (in) stop;
do forever;
get file (in) list (n); put skip list (n);
n = abs(n);
s = trim(n);
if length(s) < 3 then put list ('not possible');
else if mod(length(s), 2) = 0 then put list ('not possible');
else
do;
do while (length(s) > 3);
s = substr(s, 2, length(s)-2);
end;
put list ('The middle three digits are: ' || s);
end;
end;
end middle; </lang> Output:
123 The middle three digits are: 123
12345 The middle three digits are: 234
1234567 The middle three digits are: 345
987654321 The middle three digits are: 654
10001 The middle three digits are: 000
-10001 The middle three digits are: 000
-123 The middle three digits are: 123
-100 The middle three digits are: 100
100 The middle three digits are: 100
-123451 not possible
2 not possible
-1 not possible
-10 not possible
2002 not possible
-2002 not possible
0 not possible
Prolog
<lang prolog> middle_3_digits(Number, [D1,D2,D3]) :-
verify_middle_3_able(Number, Digits), append(FrontDigits, [D1,D2,D3| BackDigits], Digits), same_length(FrontDigits, BackDigits).
verify_middle_3_able(Number, Digits) :-
must_be(number, Number),
AbsNumber is abs(Number),
number_chars(AbsNumber, Digits),
length(Digits, NumDigits),
( 3 > NumDigits -> domain_error('at least 3 digits', Number)
; 0 is NumDigits mod 2 -> domain_error('odd number of digits', Number)
; true
).
</lang>
Test code:
<lang prolog> test_correct :-
TestCases = [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345],
foreach( ( member(TestCase, TestCases),
middle_3_digits(TestCase, Result) ),
format('Middle 3 digits of ~w ~30|: ~w~n', [TestCase, Result])
).
</lang>
Testing correct inputs:
?- test_correct. Middle 3 digits of 123 : [1,2,3] Middle 3 digits of 12345 : [2,3,4] Middle 3 digits of 1234567 : [3,4,5] Middle 3 digits of 987654321 : [6,5,4] Middle 3 digits of 10001 : [0,0,0] Middle 3 digits of -10001 : [0,0,0] Middle 3 digits of -123 : [1,2,3] Middle 3 digits of -100 : [1,0,0] Middle 3 digits of 100 : [1,0,0] Middle 3 digits of -12345 : [2,3,4] true.
Errors
?- middle_3_digits(1, S). ERROR: Domain error: `at least 3 digits' expected, found `1' ?- middle_3_digits(2, S). ERROR: Domain error: `at least 3 digits' expected, found `2' ?- middle_3_digits(-1, S). ERROR: Domain error: `at least 3 digits' expected, found `-1' ?- middle_3_digits(-10, S). ERROR: Domain error: `at least 3 digits' expected, found `-10' ?- middle_3_digits(2002, S). ERROR: Domain error: `odd number of digits' expected, found `2002' ?- middle_3_digits(-2002, S). ERROR: Domain error: `odd number of digits' expected, found `-2002' ?- middle_3_digits(0, S). ERROR: Domain error: `at least 3 digits' expected, found `0'
Python
<lang python>>>> def middle_three_digits(i): s = str(abs(i)) length = len(s) assert length >= 3 and length % 2 == 1, "Need odd and >= 3 digits" mid = length // 2 return s[mid-1:mid+2]
>>> passing = [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345] >>> failing = [1, 2, -1, -10, 2002, -2002, 0] >>> for x in passing + failing: try: answer = middle_three_digits(x) except AssertionError as error: answer = error print("middle_three_digits(%s) returned: %r" % (x, answer))
middle_three_digits(123) returned: '123'
middle_three_digits(12345) returned: '234'
middle_three_digits(1234567) returned: '345'
middle_three_digits(987654321) returned: '654'
middle_three_digits(10001) returned: '000'
middle_three_digits(-10001) returned: '000'
middle_three_digits(-123) returned: '123'
middle_three_digits(-100) returned: '100'
middle_three_digits(100) returned: '100'
middle_three_digits(-12345) returned: '234'
middle_three_digits(1) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(2) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(-1) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(-10) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(2002) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(-2002) returned: AssertionError('Need odd and >= 3 digits',)
middle_three_digits(0) returned: AssertionError('Need odd and >= 3 digits',)
>>> </lang>
Racket
<lang scheme>#lang racket (define (middle x)
(cond
[(negative? x) (middle (- x))]
[(< x 100) "error: number too small"]
[else
(define s (number->string x))
(define l (string-length s))
(cond [(even? l) "error: number has even length"]
[else (define i (quotient l 2))
(substring s (- i 1) (+ i 2))])]))
(map middle (list 123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345)) (map middle (list 1 2 -1 -10 2002 -2002 0))</lang> The output: <lang scheme>'("123" "234" "345" "654" "000" "000" "123" "100" "100" "234") '("error: number too small" "error: number too small" "error: number too small" "error: number too small"
"error: number has even length" "error: number has even length" "error: number too small")</lang>
REXX
version 1
<lang rexx>/* REXX ***************************************************************
- 03.02.2013 Walter Pachl
- 19.04.2013 mid 3 is now a function returning the middle 3 digits
- or an error indication
- /
sl='123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345',
'2 -1 -10 2002 -2002 0 abc 1e3 -17e-3'
Do While sl<> /* loop through test values */
Parse Var sl s sl /* pick next value */ Say left(s,12) '->' mid3(s) /* test it */ End
Exit
mid3: Procedure Parse arg d /* take the argument */ Select /* first test for valid input */
When datatype(d)<>'NUM' Then Return 'not a number'
When pos('E',translate(d))>0 Then Return 'not just digits'
When length(abs(d))<3 Then Return 'less than 3 digits'
When length(abs(d))//2<>1 Then Return 'not an odd number of digits'
Otherwise Do /* input is ok */
dx=abs(d) /* get rid of optional sign */
ld=length(dx) /* length of digit string */
z=(ld-3)/2 /* number of digits to cut */
res=substr(dx,z+1,3) /* get middle 3 digits */
End
End
Return res</lang>
Output:
123 -> 123 12345 -> 234 1234567 -> 345 987654321 -> 654 10001 -> 000 -10001 -> 000 -123 -> 123 -100 -> 100 100 -> 100 -12345 -> 234 2 -> less than 3 digits -1 -> less than 3 digits -10 -> less than 3 digits 2002 -> not an odd number of digits -2002 -> not an odd number of digits 0 -> less than 3 digits abc -> not a number 1e3 -> not just digits -17e-3 -> not just digits
version 2
A premise: 12.3e2 is an integer (regardless of how it's displayed).
So is the value of a googol and a googleplex.
This REXX version is limited to numbers whose absolute value ≤ 100,000 digits.
(The limit is defined via the NUMERIC DIGITS statement.)
<lang rexx>/*REXX program returns the 3 middle digits of a number (or an error). */
n ='123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345',
'2 -1 -10 2002 -2002 0 abc 1e3 -17e-3 1234567. 1237654.00', '1234567890123456789012345678901234567890123456789012345678901234567'
do j=1 for words(n); z=word(n,j) /* [↓] format the output nicely.*/
say 'middle 3 digits of' right(z,max(15,length(z))) '──►' middle3(z)
end /*j*/
exit /*stick a fork in it, we're done.*/ /*──────────────────────────────────MIDDLE3 subroutine──────────────────*/ middle3: procedure; arg x; numeric digits 1e5; er=' ***error!*** ' if datatype(x,'N') then x=abs(x); L=length(x) if \datatype(x,'W') then return er "arg isn't an integer" if L<3 then return er "arg is less than three digits" if L//2==0 then return er "arg isn't an odd number of digits"
return substr(x, (L-3)%2+1, 3)</lang>
output
middle 3 digits of 123 ──► 123 middle 3 digits of 12345 ──► 234 middle 3 digits of 1234567 ──► 345 middle 3 digits of 987654321 ──► 654 middle 3 digits of 10001 ──► 000 middle 3 digits of -10001 ──► 000 middle 3 digits of -123 ──► 123 middle 3 digits of -100 ──► 100 middle 3 digits of 100 ──► 100 middle 3 digits of -12345 ──► 234 middle 3 digits of 2 ──► ***error!*** arg is less then three digits middle 3 digits of -1 ──► ***error!*** arg is less then three digits middle 3 digits of -10 ──► ***error!*** arg is less then three digits middle 3 digits of 2002 ──► ***error!*** arg isn't an odd number of digits middle 3 digits of -2002 ──► ***error!*** arg isn't an odd number of digits middle 3 digits of 0 ──► ***error!*** arg is less then three digits middle 3 digits of abc ──► ***error!*** arg isn't an integer middle 3 digits of 1e3 ──► ***error!*** arg isn't an odd number of digits middle 3 digits of -17e-3 ──► ***error!*** arg isn't an integer middle 3 digits of 1234567. ──► 345 middle 3 digits of 1237654.00 ──► 376 middle 3 digits of 1234567890123456789012345678901234567890123456789012345678901234567 ──► 345
Ruby
<lang ruby>def middle_three_digits(num)
# minus sign doesn't factor into digit count, # and calling #abs acts as a duck-type assertion num = num.abs # convert to string and find length length = (str = num.to_s).length # check validity raise ArgumentError, "Number must have at least three digits" if length < 3 raise ArgumentError, "Number must have an odd number of digits" if length.even? return str[length/2 - 1, 3].to_i
end</lang>
Testing program:
<lang ruby>samples = [
123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0
]
left_column_width = samples.map { |n| n.to_s.length }.max samples.each do |n|
print "%#{left_column_width}d: " % n
begin
puts "%03d" % middle_three_digits(n)
rescue ArgumentError => e
puts e
end
end</lang>
- Output:
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1: Number must have at least three digits
2: Number must have at least three digits
-1: Number must have at least three digits
-10: Number must have at least three digits
2002: Number must have an odd number of digits
-2002: Number must have an odd number of digits
0: Number must have at least three digits
Rust
<lang d>// rust 0.8
fn middle_three_digits(x: int) -> Result<~str, ~str> {
let s = x.abs().to_str();
let len = s.len();
if len < 3 {
Err(~"Too short")
} else if len % 2 == 0 {
Err(~"Even number of digits")
} else {
Ok(s.slice(len/2 - 1, len/2 + 2).to_owned())
}
}
fn print_result(x: int) {
print!("middle_three_digits({}) returned: ", x);
match middle_three_digits(x) {
Ok(s) => println!("Success, {}", s),
Err(s) => println!("Failure, {}", s)
}
}
fn main() {
let passing = [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345];
let failing = [1, 2, -1, -10, 2002, -2002, 0];
for i in passing.iter() {
print_result(*i);
}
for i in failing.iter() {
print_result(*i);
}
}</lang>
- Output:
middle_three_digits(123) returned: Success, 123 middle_three_digits(12345) returned: Success, 234 middle_three_digits(1234567) returned: Success, 345 middle_three_digits(987654321) returned: Success, 654 middle_three_digits(10001) returned: Success, 000 middle_three_digits(-10001) returned: Success, 000 middle_three_digits(-123) returned: Success, 123 middle_three_digits(-100) returned: Success, 100 middle_three_digits(100) returned: Success, 100 middle_three_digits(-12345) returned: Success, 234 middle_three_digits(1) returned: Failure, Too short middle_three_digits(2) returned: Failure, Too short middle_three_digits(-1) returned: Failure, Too short middle_three_digits(-10) returned: Failure, Too short middle_three_digits(2002) returned: Failure, Even number of digits middle_three_digits(-2002) returned: Failure, Even number of digits middle_three_digits(0) returned: Failure, Too short
Scala
<lang scala>/**
* Optionally return the middle three digits of an integer. * * @example List(123,12345,-789,1234,12) flatMap (middleThree(_)), returns: List(123, 234, 789) */
def middleThree( s:Int ) : Option[Int] = s.abs.toString match {
case v if v.length % 2 == 0 => None // Middle three is undefined for even lengths case v if v.length < 3 => None case v => val i = (v.length / 2) - 1 Some( v.substring(i,i+3).toInt )
}
// A little test...
val intVals = List(123,12345,1234567,987654321,10001,-10001,-123,-100,100,-12345,1,2,-1,-10,2002,-2002,0)
intVals map (middleThree(_)) map {
case None => "No middle three" case Some(v) => "%03d".format(v) // Format the value, force leading zeroes
} mkString("\n") </lang>
- Output:
123 234 345 654 000 000 123 100 100 234 No middle three No middle three No middle three No middle three No middle three No middle three No middle three
Seed7
<lang seed7>$include "seed7_05.s7i";
const func string: middle3 (in integer: number) is func
result
var string: middle3 is "";
begin
middle3 := str(abs(number));
if not odd(length(middle3)) or length(middle3) < 3 then
middle3 := "error";
else
middle3 := middle3[succ((length(middle3) - 3) div 2) len 3];
end if;
end func;
const proc: main is func
local
var integer: number is 0;
var string: mid3 is "";
begin
for number range [] (123, 12345, 1234567, 987654321, 10001, -10001, -123,
-100, 100, -12345, 1, 2, -1, -10, 2002, -2002, 0) do
writeln(number <& ": " <& middle3(number));
end for;
end func;</lang>
- Output:
123: 123 12345: 234 1234567: 345 987654321: 654 10001: 000 -10001: 000 -123: 123 -100: 100 100: 100 -12345: 234 1: error 2: error -1: error -10: error 2002: error -2002: error 0: error
SQL
<lang sql>;WITH DATA
AS (SELECT CAST(ABS(NUMBER) AS NVARCHAR(MAX)) charNum,
NUMBER,
LEN(CAST(ABS(NUMBER) AS NVARCHAR(MAX))) LcharNum
FROM TABLE1)
SELECT CASE
WHEN ( LCHARNUM >= 3
AND LCHARNUM % 2 = 1 ) THEN SUBSTRING(CHARNUM, LCHARNUM / 2, 3)
ELSE 'Error!'
END Output,
NUMBER Input
FROM DATA </lang>
| OUTPUT | INPUT | |--------|-----------| | 123 | 123 | | 234 | 12345 | | 345 | 1234567 | | 654 | 987654321 | | 000 | 10001 | | 000 | -10001 | | 123 | -123 | | 100 | -100 | | 100 | 100 | | 234 | -12345 |
| OUTPUT | INPUT | |--------|-------| | Error! | 1 | | Error! | 2 | | Error! | -1 | | Error! | -10 | | Error! | 2002 | | Error! | -2002 | | Error! | 0 |
Tcl
<lang tcl>proc middleThree n {
if {$n < 0} {
set n [expr {-$n}]
}
set idx [expr {[string length $n] - 2}]
if {$idx % 2 == 0} {
error "no middle three digits: input is of even length"
}
if {$idx < 1} {
error "no middle three digits: insufficient digits"
}
set idx [expr {$idx / 2}]
string range $n $idx [expr {$idx+2}]
}</lang> Demonstrating: <lang tcl>foreach n {
123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1 -10 2002 -2002 0
} {
if {[catch {
set mid [middleThree $n]
} msg]} then {
puts "error for ${n}: $msg"
} else {
puts "found for ${n}: $mid"
}
}</lang>
- Output:
found for 123: 123 found for 12345: 234 found for 1234567: 345 found for 987654321: 654 found for 10001: 000 found for -10001: 000 found for -123: 123 found for -100: 100 found for 100: 100 found for -12345: 234 error for 1: no middle three digits: insufficient digits error for 2: no middle three digits: insufficient digits error for -1: no middle three digits: insufficient digits error for -10: no middle three digits: input is of even length error for 2002: no middle three digits: input is of even length error for -2002: no middle three digits: input is of even length error for 0: no middle three digits: insufficient digits
UNIX Shell
<lang bash>function middle3digits {
typeset -i n="${1#-}"
typeset -i l=${#n}
if (( l < 3 )); then
echo >&2 "$1 has less than 3 digits"
return 1
elif (( l % 2 == 0 )); then
echo >&2 "$1 has an even number of digits"
return 1
else
echo ${n:$((l/2-1)):3}
return 0
fi
}
- test
testdata=(123 12345 1234567 987654321 10001 -10001 -123 -100 100 -12345 1 2 -1
-10 2002 -2002 0)
for n in ${testdata[@]}; do
printf "%10d: " $n middle3digits "$n"
done</lang>
Output:
123: 123
12345: 234
1234567: 345
987654321: 654
10001: 000
-10001: 000
-123: 123
-100: 100
100: 100
-12345: 234
1: 1 has less than 3 digits
2: 2 has less than 3 digits
-1: -1 has less than 3 digits
-10: -10 has less than 3 digits
2002: 2002 has an even number of digits
-2002: -2002 has an even number of digits
0: 0 has less than 3 digits
Vedit macro language
<lang vedit>do {
#1 = Get_Num("Enter a number, or 0 to stop: ", STATLINE)
Ins_Text("Input: ") Num_Ins(#1, COUNT, 10)
Call("MIDDLE_3_DIGITS")
Ins_Text(" Result: ") Reg_Ins(10) Ins_Newline
Update()
} while (#1); Return
// Find middle 3 digits of a number // in: #1 = numeric value // out: @10 = the result, or error text //
- MIDDLE_3_DIGITS:
Buf_Switch(Buf_Free) Num_Ins(abs(#1), LEFT+NOCR) // the input value as string
- 2 = Cur_Col-1 // #2 = number of digits
if (#2 < 3) {
Reg_Set(10, "Too few digits!")
} else {
if ((#2 & 1) == 0) {
Reg_Set(10, "Not odd number of digits!")
} else {
Goto_Pos((#2-3)/2) Reg_Copy_Block(10, Cur_Pos, Cur_Pos+3)
}
} Buf_Quit(OK) Return </lang>
Output:
Input: 123 Result: 123 Input: 12345 Result: 234 Input: 1234567 Result: 345 Input: 987654321 Result: 654 Input: 10001 Result: 000 Input: -10001 Result: 000 Input: -123 Result: 123 Input: -100 Result: 100 Input: 100 Result: 100 Input: -12345 Result: 234 Input: 1 Result: Too few digits! Input: 2 Result: Too few digits! Input: -1 Result: Too few digits! Input: -10 Result: Too few digits! Input: 2002 Result: Not odd number of digits! Input: -2002 Result: Not odd number of digits! Input: 0 Result: Too few digits!
Wart
<lang wart>def (mid3 n)
withs (digits (with outstring # itoa
(pr abs.n))
max len.digits
mid (int max/2))
if (and odd?.max (max >= 3))
(digits mid-1 mid+2)</lang>
Output
mid3.123 => 123 mid3.12345 => 234 mid3.1234567 => 345 mid3.987654321 => 654 mid3.10001 => 000 mid3 -10001 => 000 (mid3 -123) => 123 (mid3 -100) => 100 (mid3 100) => 100 (mid3 -12345) => 234 # Errors mid3.1 => nil mid3.2 => nil mid3 -1 => nil mid3 -10 => nil mid3 2002 => nil mid3 -2002 => nil (mid3 0) => nil
XPL0
<lang XPL0>include c:\cxpl\stdlib;
func Mid3Digits(I); \Return the middle three digits of I int I; int Len, Mid; char S(10); [ItoA(abs(I), S); Len:= StrLen(S); if Len<3 or (Len&1)=0 then return "Must be 3, 5, 7 or 9 digits"; Mid:= Len/2; S:= S + Mid - 1; S(2):= S(2) ! $80; \terminate string return S; \WARNING: very temporary ];
int Passing, Failing, X; [Passing:= [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345];
Failing:= [1, 2, -1, -10, 2002, -2002, 0]; \WARNING: nasty trick
for X:= 0 to 16 do
[Text(0, "Middle three digits of "); IntOut(0, Passing(X));
Text(0, " returned: ");
Text(0, Mid3Digits(Passing(X))); CrLf(0);
];
]</lang>
- Output:
Middle three digits of 123 returned: 123 Middle three digits of 12345 returned: 234 Middle three digits of 1234567 returned: 345 Middle three digits of 987654321 returned: 654 Middle three digits of 10001 returned: 000 Middle three digits of -10001 returned: 000 Middle three digits of -123 returned: 123 Middle three digits of -100 returned: 100 Middle three digits of 100 returned: 100 Middle three digits of -12345 returned: 234 Middle three digits of 1 returned: Must be 3, 5, 7 or 9 digits Middle three digits of 2 returned: Must be 3, 5, 7 or 9 digits Middle three digits of -1 returned: Must be 3, 5, 7 or 9 digits Middle three digits of -10 returned: Must be 3, 5, 7 or 9 digits Middle three digits of 2002 returned: Must be 3, 5, 7 or 9 digits Middle three digits of -2002 returned: Must be 3, 5, 7 or 9 digits Middle three digits of 0 returned: Must be 3, 5, 7 or 9 digits
zkl
<lang zkl>fcn middle(ns){
ns.apply("toString").apply('-("-"))
.apply(fcn(n){nl:=n.len();
if(nl<3 or nl.isEven) return(False);
n[(nl-3)/2,3] : "%03d".fmt(_)
})
} middle(T(123,12345,1234567,987654321,10001,-10001,-123,-100,100,-12345)).println() middle(T(1, 2, -1, -10, 2002, -2002, 0)).println();</lang>
- Output:
L("123","234","345","654","000","000","123","100","100","234")
L(False,False,False,False,False,False,False)
Algorithm is convert each number into a string, remove any "-", reject strings less then 3 characters or are even in length, return middle three characters of remainder.
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